••••I 

£&      EHHHBBBBBB^DBHHBfll 


State  Mining  Bureau. 

/ 

HENR  Y  G.  HANKS,  State  Mineralogist. 


CONTRIBUTIONS 


TO  THE 


Geology  and  Mineralogy 


OF 


CALIFORNIA. 


ON  THE  MILLING  OF  GOLD  QUARTZ, 


By  MELVILLE  ATT  WOOD,  R   G.  S. 


SACRAMENTO  : 

J.    D.    YOUNG,     ::::::     SUPT.    STATE   PRINTING 
1882. 


State  Mining  Bureau 

HENR  Y  G.  HANKS,  State  Mineralogist. 

CONTRIBUTIONS 


TO  THE 


Geology  and  Mineralogy 


OF 


CALIFORNIA. 

ON  THE  MILLING  OF  GOLD  QUARTZ, 

Bv  MELVILLE  ATT  WOOD,  F.   G.  S. 


SACRAMENTO  : 

j.  D.  YOUNG,    :::::::    SUPT.  STATE  PRINTING, 
1882. 


• 


On  the  Milling  of  Gold  Quartz. 


HENRY  G.  HANKS,  State  Mineralogist: 

DEAR  SIR  :  My  last  paper  to  the  State  Geological  Society 
on  "  The  Milling  of  Gold  Quartz,"  wherein  I  tried  to  describe 
the  process  of  simple  amalgamation  of  the  raw  pyritic  matter 
in  wooden  barrels,  appears  from  the  great  number  of  letters 
that  I  have  received  respecting  it,  after  its  publication  in  the 
Mining  and  Scientific  Press,  to  have  attracted  considerable 
attention,  and  has,  therefore,  encouraged  me  to  resume  the 
subject,  but  this  time  as  a  contribution  to  the  State  Mining 
Bureau  ;  you  having  kindly  offered  to  allow  the  specimens 
accompanying  this  paper,  and  intended  to  illustrate  what  I 
have  stated,  to  remain  for  a  short  time  at  the  rooms  of  the 
Mining  Bureau,  to  give  those  who  feel  interested  in  the  mat- 
ter a  chance  of  examining  them.  You  have  also  promised  to 
put  some  very  important  and  interesting  specimens  from 
your  private  collection  with  them. 

I  can  only  now  repeat  what  I  have  stated  on  a  former 
occasion,  that  at  the  present  time  I  think  scarcely  anything 
can  be  of  greater  importance  to  the  mining  interests  of  this 
State,  than  a  simple  and  cheap  mode  of  extracting  the  gold 
from  low  grade  veinstone,  and  the  determination  of  the  true 
condition  of  the  ores  associated  with  it. 

THE   "FREE   GOLD," 

As  it  is  called,  can  easily  be  saved  ;  indeed,  the  language  of 
the  old  mill-man,  "  only  give  it  a  chance  and  it  will  take  care 
of  itself,"  is  very  true,  particularly  so  when  met  with,  as  it  is 
in  some  of  the  Bodie  veins,  carrying  scarcely  any  pyritic 
matter.  The  difficulty  in  the  concentration  of  the  sulphurets 
(I  use  the  Californian  term,  which,  as  I  stated  before,  was,  I 
think,  first  applied  in  Nevada  County,  in  1859,  to  the  pyritic 
matter  associated  with  the  quartz  in  the  gold-bearing  veins 

242648 


-  4  - 

of  this  State),  appears  now  to  be,  in  a  great  measure,  over- 
come by  the  use  of  the '  "  Frue  concentrator,"  which,  with 
comparatively  little  attention,  and  at  one  operation,  makes 
very  clean  work.  I  have  served  a  very  long  apprenticeship 
in  the  "dressing"  of  different  kinds  of  ores,  but  in  all  my 
experience  never  remember  any  machine  which  pleased  me 
better  than  the  "  Frue."  The  rubber  surface  of  the  revolving 
cloth  appears  to  greatly  assist  the  operation. 

The  question  of  concentration  being  now  so  far  solved,  it 
renders  it  desirable,  indeed  necessary,  for  isolated  mills  to 
have  some  cheap  and  easy  mode,  which  they  can  use  at  their 
own  works,  to  extract  the  gold  from  the  concentrations. 

TREATING    PYRITES    FOR    THE    EXTRACTION    OF    ITS    GOLD. 

The  following  is  a  copy  of  a  paper  on  "  Iron  Pyrites,"  read 
before  the  Royal  Society  of  New  South  Wales,  in  1874,  by 
J.  Latta,  Esq.,  which  contains  much  valuable  information  : 

MR.  PRESIDENT  AND  GENTLEMEN  :  At  the  request  of  some  of 
the  members  of  the  Royal  Society,  I  have  ventured  to  occupy  part 
of  your  time  this  evening  in  describing  the  method  of  treating  pyrites 
for  the  extraction  of  its  gold,  as  carried  out  by  the  Port  Phillips 
Company,  at  Clunes. 

In  1 86 1  I  was  engaged  by  that  company  as  their  chemist  and 
assayer,  with  special  instructions  to  devise,  if  possible,  a  process  for 
profitably  extracting  the  gold  from  their  pyrites,  which  was  then  but 
little  better  than  a  waste  product.  Except  processes  inapplicable  to 
our  circumstances,  such  as  smelting,  etc.,  the  only  known  means  for 
extracting  gold  from  such  mineral  was  that  practiced  in  South 
America  and  the  United  States — "  of  exposing  the  auriferous  sul- 
phides to  the  action  of  air  and  moisture  for  a  year  or  so,  whereby  a 
portion  of  the  mineral  became  oxidized,  liberating  the  gold  previously 
inclosed  by  the  sulphides ;  the  mineral  was  then  passed  through  the 
stamping  battery  with  quartz,  and  whatever  portion  of  the  sulphides 
remained  undecomposed  was  retained,  as  well  as  the  then  rude 
machinery  for  that  purpose  admitted,  to  undergo  another  term  of 
oxidation,  and  so  on  whilst  any  remained."  I  scarcely  need  to  point 
out  how  extravagantly  wasteful  of  time  and  gold  such  a  process  must 
have  been.  Yet  even  at  the  present  time  this  process  is  occasionally 
practiced  in  Victoria.  At  some  claims  the  blanketings — that  is,  the 
pyritous  sand,  with  a  little  free  gold  caught  upon  the  blankets — are, 
after  a  time,  again  put  through  the  batteries  with  the  quartz,  for  the 
purpose  of  extracting  its  gold.  Any  one  practically  acquainted  with 
the  treatment  of  mineral  containing  fine  gold  by  the  battery  process, 
will  at  once  recognize  the  impossibility  of  retaining  a  fair  proportion 
of  such  minutely  divided  gold  as  oxidized  pyrites  affords ;  by  far  the 


larger  portion  would  be  held  in  suspension  by  the  water,  and  be 
carried  away  by  it  through  all  the  appliances  devised  for  its  retention. 
In  addition  to  the  difficulty  of  retention  arising  from  the  fine  state  of 
division  which  gold  so  obtained  possesses,  most  of  these  particles 
would  be 

COATED    WITH    IRON    OXIDE, 

and  other  products  of  the  decomposed  mineral,  thus  offering  another 
hindrance  to  its  chance  of  amalgamating  with  the  mercury.  This 
latter  difficulty  deserves  careful  consideration,  where  fine  gold  has  to 
be  dealt  with,  as  from  its  fineness  it  escapes  the  scrubbing  which  the 
larger  grains  receive  from  contact  with  the  quartz  whilst  crushing, 
whereby  their  surfaces  are  cleaned,  and  thus  rendered  extremely 
sensitive  to  the  influence  of  mercury  placed  for  their  detention.  In 
reference  to  the  condition  of  the  gold  in»pyrites,  it  li£,s  come  to  be 
pretty  generally  admitted  that  'nearly,  if  not  quite,  all  the  gold  exists 
in  the  metallic  state.'  " 

This  qui^te  agrees  with  the  results  of  some  experiments  carried  out 
by  myself  in  conjunction  with  Mr  Daintree,  late  of  the  Victoria  geo- 
logical staff.  Our  researches  ended  in  obtaining  but  the  barest  pos- 
sible evidence  of 

GOLD     EXISTING    IN    A    MINERALIZED    STATE    IN    PYRITES. 

As  a  matter  bearing  somewhat  in  support  of  this  result,  and  whilst 
engaged  in  these  investigations,  I  had  the  good  fortune  to  come 
across  some  fine  specimens  of  cubical  pyrites,  which  upon  examina- 
tion with  a  pocket  lens,  seemed  to  indicate  the  presence  of  gold ; 
upon  transferring  them  to  a  good  microscope,  gold  was  distinctly  seen 
upon  the  planes  of  cleavage,  and  upon  dissecting  the  crystals,  every 
cleavage  face  was  found  distinctly  gilded.  Now,  from  the  fact  that 
the  presence  of  gold  could  only  be  determined  by  the  aid  of  a  good 
microscope,  and  that  only  as  a  fine  gilding,  some  notion  may  be 
formed  of  the  excessively  fine  state  of  its  division,  and  how  unsatis- 
factory would  be  the  task  of  separating  such  liberated  films  from* 
water  in  motion. 

Guided  by  these  considerations  it  became  evident  that  any  attempt 
to  mechanically  separate  gold  from  pyrite — unless  aided  by  the 
previous  decomposition  of  its  enveloping  sulphides — must  prove 
ineffective  from  the  impossibility  of  reducing  it  to  its  ultimate  atoms, 
for  so  long  as  a  cluster  of  sulphide  atoms  remain  unbroken,  they 
might  reasonably  be  imagined  to  enclose  those  of  gold.  Again,  it 
was  equally  clear  that,  when  such  gold  was  liberated  from  its  enve- 
lope, water  concentration  alone  was  inapplicable.  To  test  the  cor- 
rectness of  these  conclusions,  each  of  them  was  made  the  subject  of 
rigid  experiment  on  an  extended  scale, .  before  receiving  them  as 
fundamental  truths  to  guide  us  in  determining  the  best  method 
suitable  to  our  requirements.  Two  parcels  of  pyrites  of  twenty  tons 


-  6  - 

each — one  roasted,  the  other  unroasted — were  ground  in  one  of  the 
best  arastras  known,  with  mercury ;  a  constant  stream  of  water  flow- 
ing through  to  carry  off  the  finely  ground  sand,  which  was  then 
carried  through  mercury  boxes  and  over  blankets.  Each  parcel 
received  the  same  amount  of  grinding  and  treatment  in  every  detail. 
The  results  are  as  follows : 

Twenty  tons  raw  sand  containing  3  oz.  6  dwts.  per  ton: 

Gold  obtained 29.21  per  cent. 

Gold  in  tailings 42.84  per  cent. 

Gold  carried  off  in  water 27.95  per  cent. 

Twenty  tons  roasted  sand,  1  oz.  7  dwts.  10  grs.  of  gold  per  ton: 

Gold  obtained 51.57  per  cent. 

Gold  in  tailings 27.21  per  cent. 

Gold  carried  off  by  water 21.22  percent. 

Here  it  will  be  observed  that,  with  the  raw  sand,  only  a  small  por- 
tion of  the  gold  was  obtained— a  very  much  larger  was  left  in  the 
tailings,  although  finely  ground,  and  a  large  proportion  was  carried 
off  with  the  water  as  slime.  With  the  roasted  mineral  more  than 
half  the  gold  was  obtained ;  the  tailings  were  much  poorer  than 
those  from  the  raw  sand,  but  still  very  rich,  and  a  large  quantity  was 
carried  off  by  the  water. 

After  carefully  considering  the  merits  of  the  various  methods  sug- 
gested for  extracting  gold  from  pyrites,  our  first  problem  to  solve  was 
how  to  best  destroy  the  enveloping  sulphides  and  arsenides,  so  as  to 
get  rid  of  the  deleterious  action  of  these  minerals  upon  the  mer- 
cury used  for  amalgamating  and  detaining  the  liberated  gold;  and, 
secondly,  the  best  method  of  extracting  the  gold  from  the  decom- 
posed pyrites.  After  a  number  of  experiments  on  a  large  scale,  it 
was  decided  to  effect  the  decomposition  of  the  pyrites  by  a  roasting 
process.  To  effect  this  economically,  I  devised,  and,  in  conjunction 
with  Mr.  H.  A.  Thompson,  patented,  in  1862,  the  inclined  roasting 
furnace,  which  is  now  used  in  many  places  throughout  the  Colonies. 
It  consists  of  an  inclined  roasting  hearth,  usually  about  30  feet  long 
'by  5  feet  wide;  the  fire-hole  for  heating  the  hearth  on  the  lower  end 
of  it,  and  is  separated  from  it  by  the  fire  bridge;  between  the  latter 
and  the  hearth  is  a  channel  for  conveying  into  the  store-pit  the  sand 
when  roasted.  In  the  foot  wall  of  the  furnace  are  6  tubes,  from  i^ 
to  2  inches  diameter,  for  supplying  heated  air  to  the  roasting  sul- 
phides; scarcely  any  air  is  admitted  through  the  fire  bars,  the  gas- 
eous vapors  from  the  fuel  being  completely  burned  by  the  great 
excess  of  air  passing  over  the  fire  for  oxydizing  the  pyrites.  Along 
each  side  of  the  furnace  are  five  working  doors,  for  the  workmen  to 
turn  and  rake  down  the  mineral.  Above  the  upper  end  of  the  fur- 
nace a  large  hopper  is  constructed,  capable  of  holding  24  hours' 
supply  of  sand;  in  the  floor  of  this  hopper  is  a  trap  for  supplying 
mineral  to  the  hearth ;  the  hopper  is  filled  by  trucks  communicating 
with  the  puddles  by  a  tramway  to  the  stamp-house.  The  whole  of 


-  7  - 

the  furnace  is  carefully  braced  with  vertical,  longitudinal,  and  trans- 
verse ties.  The  present  furnace  has  been  working  about  ten  years, 
and,  with  fair  treatment,  will  last  many  years  more.  In  working  this 
furnace  the  whole  of  the  hearth  is  covered  with  pyrites  to  the  depth 
of  between  2  and  3  inches,  kept  at  a  gentle  red  heat,  with  frequent 
stirring,  until  the  mineral  nearest  the  fire,  and  about  6  feet  beyond 
it,  is  found  no  longer  to  give  off  sulphur  fumes.  An  experienced 
workman  can  determine  when  this  condition  has  been  attained  by  its 
appearance  in  the  furnace.  It  is  then  raked  into  the  discharge  chan- 
nel and  the  mineral  lying  upon  the  hearth  immediately  above  that 
removed,  is  brought  into  its  place ;  again,  that  still  further  up  is 
brought  a  stage  lower,  until  the  whole  has  been  shifted,  when  the 
vacant  place  at  the  upper  part  is  refilled  from  the  hopper.  The 
sulphurous  and  arsenical  vapors,  together  with  the  products  of  com- 
bustion and  dust  from  the  pyrites,  pass  jnto  a  tunnel  between  200 
and  300  feet  long,  4  feet  high,  and  3  feet  wide,  carried  up  the  side 
of  a  hill,  terminating  in  a  chimney  30  feet  high.  Nearly  all  the  sand 
and  dust  carried  over  by  the  draft  is  deposited  within  40  feet  of  the 
furnace,  and  is  periodically  removed  for  retreatment,  as  it  contains  a 
notable  quantity  of  gold;  beyond  40  feet  the  sand  is  worthless.  From 
the  size  of  the  tunnel  the  vapors  move  slowly  onward,  and  have, 
consequently,  time  to  deposit  any  heavy  particles;  continuing  their 
course,  the  vapors  pass  through  6  cellular  brick  screens,  down  which 
a  powerful  spray  of  water  passes;  here  they  get  cooled  and  scrubbed, 
the  sulphurous  and  sulphuric  acids  dissolved  out,  whilst  the  arsen- 
ious  acid  is  deposited  on  the  floor  of  the  tunnel,  scarcely  anything 
escaping  from  the  chimney  but  the  foul  vapors.  Some  alarm  was 
felt  by  the  Town  Council  lest  any 

ARSENICAL    VAPORS 

Should  escape  and  prove  injurious  to  the  inhabitants,  as  the  works 
were  close  upon  the  township,  and  they  placed  the  matter  in  the 
hands  of  Mr.  Johnson,  the  Government  analytical  chemist,  for  inves- 
tigation, who  reported  as  follows:  "I  drew  five  gallons  of  the  vapors 
from  the  chimney  of  the  roasting  furnace,  and,  by  the  application  of 
one  of  the  most  delicate  tests  known  to  science,  viz.,  Reinck's  test, 
discovered  but  the  merest  trace  of  arsenic."  I  may  remark  that 
when  this  investigation  took  place  we  were  condensing  over  two  tons 
of  arsenic  per  month  in  the  tunnel.  I  have  dwelt  somewhat  length- 
ily upon  this  part  of  my  subject,  as  I  am  desirous  to  show  that,  with 
due  'precautions,  such  operations  can  be  safely  carried  on.  in  the 
neighborhood  of  habitations. 

In  carrying  out  the  roasting  operations  the  work  is  divided  into 
three  shifts  of  eight  hours  each,  one  man  being  able  to  attend  a  fur- 
nace, and  finally  to  cover  up  the  hot  sand  discharged  with  damp 
sand  and  spray  it  with  water.  This  quenching  was  found  to  be  a 
matter  of  some  importance,  as  the  quartz  sand — always  found  with 


-  8  - 

the  pyrites — is  thereby  broken  up  and  rendered  friable,  by  which  the 
after  process  of  grinding  is  greatly  facilitated.  The  quantity  of  sand 
which  a  furnace  of  the  above-mentioned  size  can  treat,  will  average 
4  tons  per  24  hours,  with  a  consumption  of  3-10  of  a  cord  of  wood 
per  ton.  Having  determined  upon  a 

MECHANICAL    PROCESS    FOR    EXTRACTING  THE    GOLD 

From  the  roasting  mineral,  it  became  necessary  to  discover  the  best 
condition  for  accomplishing  it.  In  this,  also,  we  were  greatly  assisted 
by  the  knowledge  gained  of  the  physical  condition  of  the  gold  in 
pyrites.  Consequently,  after  our  earlier  experiments  already  men- 
tioned, we  carefully  avoided  a  current  of  water,  and  ground  with 
mercury  without  an  overflow  until  it  was  considered  the  gold  had 
become  amalgamated.  By  cautiously  varying  the  experiments,  and 
ascertaining  the  proportion  of  gold  obtained  in  each  case,  we  were 
led  up  to  the  present  method  of  working.  From  the  results  of  a 
great  number  of  experiments,  it  was  shown  that  the  quantity  of  water 
used  in  the  grinding  process  was  a  matter  of  considerable  importance, 
the  success  of  the  operation  to  a  great  extent  depending  upon  the 
sand  being  in  a  damp  condition  only;  by  this  means  the  mercury 
becomes  thoroughly  diffused,  and  every  grain  of  sand  has  a  particle 
of  mercury  in  contact  with  it ;  consequently  there  is  afforded  abun- 
dant opportunity  for  the  gold  to  amalgamate.  On  the  other  hand,  if 
sufficient  water  has  been  used  to  convert  the  mass  into  a  semi-fluid 
state,  the  mercury  remained  at  the  bottom  of  the  mill,  the  surface 
only  being  in  contact  with  the  sand;  consequently  the  opportunity 
for  amalgamation  was  considerably  lessened,  and  the  quantity  of  gold 
extracted  very  much  less  than  when  working  damp  sand  only.  As 
the  result  of  these  experiments,  the  following  process  has  been 
adopted :  The  sand,  after  being  roasted,  is  ground  —only  moderately 
damp — with  an  equal  weight  of  mercury  for  three  quarters  of  an 
hour,  under  the  rollers  of  an  ordinary  Chilean  mill;  water  is  then 
allowed  to  flow  into  the  basin,  the  mill  still  revolving,  until  nearly  all 
the  finely  ground  sand  has  been  carried  off  in  the  overflow  to  the 
concentrator;  the  mill  is  then  stopped,  the  water  drained  off  from 
the  unground  sand  and  mercury,  again  started,  and  recharged  with 
fresh  sand,  and  so  on  until  it  is  necessary  to  clear  out  the  amalgam—- 
generally once  a  week,  depending  upon  the  richness  of  the  mineral 
treated.  The  finely  ground  sand  passed  into  the  concentrator  is  kept 
slowly  stirred  for  a  quarter  of  an  hour,  to  keep  the  sand  in  suspen- 
sion in  the  water,  and  allow  the  mercury  and  any  amalgam  which 
might  have  been  carried  over  from  the  mill  to  gravitate  through  it; 
the  water  with  its  sand  is  then  slowly  run  through  a  smaller  concen- 
trator, to  retain  any  valuable  particles  which  might  have  escaped  the 
first,  and  is  then  .considered  sufficiently  impoverished  to  be  allowed 
to  run  away. 

The  quantity  of  roasted  mineral  the  company  treat  by  this  process, 


-  9  -      . 

when  working,  averages  18  tons  per  week — the  duty  of  two  mills 
worked  in  eight-hour  shifts,  one  man  attending  them,  alternately 
changing  and  discharging. 

THE  AVERAGE  PROPORTION  OF  GOLD  EXTRACTED 

During  the  last  year,  from  294  tons  of  pyrites,  amounted  to  95.19 
per  cent,  of  the  assays,  the  sand  averaging  4^  ounces  of  gold  per 
ton.  Some  of  the  parcels  returned  as  high  as  98  per  cent,  during 
that  period.  The  cost  of  extraction  amounted  to  £2  2s.  4d.  per 
ton,  without  estimating  wear  and  interest  on  capital.  The  above 
charge  is  rather  high,  as  fuel  during  that  period  was  unusually  dear, 
and  the  furnace  being  but  4  feet  wide,  instead  of  5  feet,  increased 
the  labor  cost,  as  less  work  is  done  at  the  same  cost  than  would  be 
incurred  in  working  a  larger  furnace.  Another  element  in  the  cost 
is  the  mercury  which  is  lost,  amounting  to  i  pound  and  13  ounces 
per  ton — a  large  proportion  of  which,  I  think,  might  be  saved  by 
improved  appliances  for  that  purpose,  together  with  the  gold  con- 
tained in  it.  The  immediate  cause  of  this  loss  of  mercury  is  the 
severe  trituration  to  which  it  is  subjected  with  the  sand.  This  was 
found  indispensable,  for  whenever,  through  oversight  or  experiment, 
a  less  degree  of  trituration  was  applied  than  that  now  used,  or  the 
sand  ground  too  wet,  th£  return  of  gold  was  invariably  diminished 
by  several  per  cent. 

In  carrying  out  these  operations,  I  found  that  a  Targe  proportion 
of  galena  in  the  mineral  seriously  interfered  with  the  extraction  of 
the  gold,  but  a  small  proportion  of  the  sulphides  of  copper,  zinc, 
or  lead  produced  no  appreciable  effect. 

Taking  the  process  as  it  stands,  we  have  been  unable  to  find  one 
that  would  at  less  cost  extract  the  same  proportion  of  gold,  or  could 
be  safely  trusted  in  unskilled  hands  with  only  occasional  supervision. 

Mr.  Thompson  also  read  the  following  return : 

Returns  of  pyrites  treated  at  the  Port  Phillip  Company's  works, 
Chines,  since  October,  1866.  Minerals  treated:  1867,  215  tons,  17 
cwt;  1868,  366  tons,  9  cwt.;  1869,  401  tons,  n  cwt;  1870,  431 
tons,  9  cwt.;  1871,  561  tons,  2  cwt.;  1872,  368  tons,  6  cwt.;  1873, 
294  tons.  Gold,  contents  per  ton,  per  assay:  1867,  4  ozs.  16  dwts. 
6.93  grs.;  1868,  3  ozs.  18  dwts.  6.56  grs.;  1869,  4  ozs.  i  dwt.  19.15 
grs.;  1870,  3  ozs.  n  dwts.  4.34  grs.;  1871,  4  ozs.  7  dwts.  10.99  grs-j 
1872,  5  ozs.  18  dwts.  19.36  grs.;  1873,  4  ozs.  10  dwts.  16.30  grs. 

Total  gold  obtained:  1867,  960  ozs.  13  dwts.;  1868,  1,322  ozs. 
13  dwts.;  1869,  1,515  ozs.  IT  dwts.;  1870,  1,370  ozs.  4  dwts.;  1871, 
2,290  o_s.  i  dwt.;  1872,  2,031  ozs.  9  dwts.;  1873,  1,268  ozs.  17 
dwts.  12  grs. 

Gold  extracted,  per  ton:    1867,  4  ozs.   9  dwts.;   1868,  3  ozs.  12 


-   IO  - 

dwts.  4  grs.;  1869,  3  ozs.  15  dwts.  11.60  grs.;  1870,  3  ozs.  3  dwts. 
12.60  grs.;  1871,  4  ozs.  i  dwt.  15.20  grs.;  1872,  5  ozs.  n  dwts. 
22.56  grs.;  1873,  4  ozs.  6  dwts.  7.63  grs. 

Percentage  of  gold  extracted:  1867,  92.43;  1868,  91.71;  1869, 
92.28;  1870,89.24;  1871,93.34;  1872,94.22;  1873,95.19. 

The  results  obtained  by  Mr.  Latta  appear  to  have  been 
exceedingly  close  and  satisfactory,  though  rather  costly— 
about  ten  dollars  per  ton — which,  I  think,  could  have  been 
much  lessened  had  the  stuff  been  reduced  finer,  and  the  con- 
centration been  carried  a  little  further,  so  as  to  have  freed 
the  pyrites  from  the  excess  of  gangue  or  quartz  sand  pre- 
vious to  calcination. 

It  is  now  generally  admitted  by  metallurgists  of  any  note, 
that  the  gold  in  pyrites  exists  in  a  metallic  state,  and  it  is 
with  no  little  pleasure  that  I  am  enabled  to  practically  cor- 
roborate the  statements  of  Mr.  Latta  on  this  subject,  having 
procured  for  your  inspection  a  number  of  crystals,  and  frag- 
ments of  crystals,  of  auriferous  pyrites,  obtained  from  different 
parts  of  this  State.  They  are  mounted  on  glass  slides  for 
microscopic  examination,  as  with  a  common  lens  the  pres- 
ence of  the  gold  can  hardly  be  detected ;  but  with  a  good 
microscope,  using  an  inch  or  half  inch  objective,  it  will  be 
found  that  the  faces  of  some  of  the  crystals  are,  in  places, 
most  finely  and  beautifully  gilded,  and  that  here  and  there 
are  seen  little  specks  or  drops  of  gold  partially  imbedded  in 
the  pyrite.  The  mill-man,  after  looking  at  these  specimens, 
will  not  be  surprised  at  the  loss  sustained  in  the  wet  stamping 
of  auriferous  pyrites. 

SAMPLING    AND    ASSAYING    GOLD    QUARTZ. 

In  Phillip's  Metallurgy,  pages  166  and  167,  very  good 
directions  are  given  for  sampling  and  assaying  gold  quartz. 
For  assaying,  he  says:  "The  most  accurate  results  are 
obtained  by  carefully  washing  a  four-pound  sample  in  the 
batea.  After  having  in  this  way  concentrated  the  gold  in 
about  an  ounce  of  sand  and  pyrites,  this  residue  may  be 
either  subjected  to  assay,  or  the  sulphides  dissolved  by  nitric 
acid,  and  the  gold  extracted  by  amalgamation  with  mercury, 
which  is  subsequently  volatilized,  and  the  gold  weighed.  In 
either  case,  calculations  are  made  on  the  four-pound  sample, 
and  when  the  residue  has  been  subjected  to  fusion,  very 
accurate  results  are  obtained." 


-  1 1  - 

BARREL  AMALGAMATION. 

During  the  time  I  was  engaged  in  gold  mining  in  Brazil,  I 
stayed  for  some  time  at  the  St.  John  del  Rey  mine,  and  there 
witnessed  the  barrel  amalgamation  which  I  described  in  my 
last  paper  to  the  State  Geological  Society,  and  which  is  repro- 
duced here: 

Their  process  of  amalgamation  is  nearly  perfect,  but  the  stamping 
and  concentration  very  defective,  the  stamps  doing  but  little  duty — 
only  \y^  tons  per  head  during  the  24  hours;  their  plan  of  concen- 
tration being  principally  what  is  called  "straking,"  consisting  of  a 
number  of  fixed  inclined  trays  30  feet  in  length  and  18  inches  wide, 
with  a  fall  of  one  inch  to  the  foot.  The  trays  are  covered  for  the  first 
1 6  feet  with  bullocks'  skins  tanned  with  the  hair  on  them,  and  in 
lengths  of  2  feet  2  inches;  below  these  are  series  of  blankets  or 
baize  cloths  of  the  same  length.  The  deposit  of  sulphurets  on 
the  first  three  skins  contains  nearly  all  the  gold,  and  amounts  to 
about  0.42  of  a  cubic  foot  per  ton  of  veinstone  stamped.  It  con- 
tains about  30  ounces  of  gold  per  ton,  all  of  which,  with  the 
exception  of  one  ounce,  is  in  a  free  state;  the  ounce  of  gold  being 
mechanically  mixed  with  the  coarser  grains  of  pyrites. 

It  is  estimated  that  in  stamping  and  straking,  10  per  cent,  of 
the  total  amount  of  the  gold  is  carried  off  in  suspension  by  the 
water. 

Their  loss  in  amalgamation  is  comparatively  trifling,  as  far  as  I 
can  gather  from  their  numerous  reports,  and  will  average  less  than 
4  per  cent.;  the  loss  of  mercury  is  0.45  ounces  per  cubic  foot  of  sul- 
phurets amalgamated.  The  apparatus  employed  for  amalgamation 
of  the  sulphurets  consists  of  wooden  barrels  4  feet  in  length  and  2 
feet  5  inches  in  diameter,  having  a  capacity  of  20  cubic  feet.  The 
charge  of  sulphurets  for  each  barrel  is  one  ton  and  a  half,  free  from 
decomposition,  and  60  pounds  of  mercury.  There  is  also  a  sufficient 
amount  of  clean  water  at  the  same  time  introduced  to  give  the  slimes 
the  necessary  degree  of  fluidity  to  enable  the  globules  of  quicksilver 
formed  to  become  properly  incorporated,  without  allowing  them  to 
become  sufficiently  mobile  to  admit  of  the  settling  of  the  mercury 
and  amalgam  at  the  bottom.  The  barrels,  when  charged,  are  allowed 
to  rotate  from  20  to  30  hours,  making  18  revolutions  per  minute,  in 
accordance  with  the  state  of  the  atmosphere. 

The  contents  of  the  barrels  are  afterwards  washed  in  an  appa- 
ratus called  a  "  saxe,"  which  is  used  to  separate  the  gold  amalgam 
from  the  refuse.  In  this  country  it  might  be  perhaps  better  to 
employ  separators  the  same  as  those  used  in  the  different  pan 
mills. 

In  their  report  of  1880  the  results  of  their  trials  of 


-    12    - 
THE    COMSTOCK    PAX    SYSTEM 

Was  anything  but  satisfactory ;  indeed,  in  the  milling  for  gold  that 
system  appears  to  be  too  costly  for  low-grade  ores,  and  not  fit  for  the 
rich.  It  is  better  calculated  for  the  treatment  of  veinstone  which 
contains  in  the  ton  from  five  to  ten  ounces  of  silver,  and  that  iri  a 
suitable  mineralized  condition  as  chlorides,  etc. 

The  attempts  to  grind  the  sulphurets  when  they  contain  upwards 
of  50  per  cent,  of  pyritic  matter,  and  to  amalgamate  the  mechanic- 
ally combined  gold  inclosed  in  the  particles  of  pyrites,  at  the  same 
time  and  in  the  same  pan,  has  not  been  attended  with  success  from 
the  earliest  attempts,  some  of  which  I  witnessed  in  Brazil  in  1832, 
which  was  then  made  in  an  apparatus  being  a  modification  of  the 
Hungarian  bowl.  The  St.  John  del  Rey  sulphurets  when  ready  for 
the  barrel  contain  about  95  per  cent,  of  pyritic  matter,  and  are 
reduced  so  fine  that  90  per  cent,  of  it  will  pass  through  a  sieve 
having  100  holes  to  the  linear  inch. 

What  I  have  tried  of  the  California  sulphurets  the  pyritic  matter 
varies  from  70  per  cent,  to  90  per  cent.,  and  about  75  per  cent,  of  it 
will  pass  through  a  sieve  of  100  holes  to  the  linear  inch. 

The  following  analyses  were  made  by  John  A.  Phillips,  F.  G.  S., 
and  published  in  his  Metallurgy  of  Gold  and  Silver.  I  lately 
received  a  letter  from  him,  wherein  he  tells  me  he  is  going  to  pub- 
lish another  work  on  gold  : 

ANALYSES     OF     AURIFEROUS      CALIFORNIA      PYRITES      CONCENTRATED 
FROM    TAILINGS    BY   JOHN    A.    PHILLIPS. 


From 
Grass  Valley. 

From 
Near  Sonora. 

North  Star, 
Grass  Valley. 

Sulphur 

46.700 

37.250 

43.720 

Arsenic    _  _ 

.310 

8.490 

1.360 

Iron 

41.650 

36.540 

39.250 

Copper 

trace. 

trace. 

.220 

T               1 

Lead 

trace. 

.400 

trace. 

Gold     

.037 

.302" 

.026 

Silver 

.OS6 

) 

.012 

Cobalt 

.036 

y  Not  determined. 

.150 

Silica 

10.970 

17.150 

14.230 

Totals. 


99.703 


100.162 


98.968 


Gold__ 
Silver 


PER    TON    OF     20  CWT. 


Oz. 
12 
11 


Dwt.     Gr. 

2  0 

16  0 


Oz. 
93 


Dwt. 
13 


Gr. 
0 


Oz.      Dwt.     Gr. 
8          10  0 

3         18  0 


-  13  - 

By  careful  analysis  their  concentrations  differ  but  little 
from  those  of  some  of  the  mines  near  Sonora,  Tuolumne 
County,  CaL,  the  amount  of  arsenic  varying  from  one  to  ten 
per  cent.,  though  in  the  upper  part  of  the  St.  John  del  Rey 
mine  it  did  not  contain  so  much  arsenic  as  the  following 
analysis,  made  by  John  A.  Phillips  in  1847,  shows. 

Analysis  of  uncrushed  ores  from  the  St.  John  del  Rey 
mines,  made  by  J.  Arthur  Phillips,  in  1847  : 

Silica 16.87 

Carbonate  magnesia 12.17 

Carbonate  lime 3.01 

Sulphur  (iron  pyrites) ^ 16.78 

Iron  (iron  pyrites) 14.65 

Peroxide  of  iron 32.84 

Peroxide  of  manganese 3.63 

Arsenic  and  gold Traces. 


99.94 
N.  B. — Gold  per  ton  equal  1  oz.  2  dwt.  20  gr. 

The  reason  I  have  said  so  much  about  these  mines,  and 
called  your  attention  so  frequently  to  them,  is  from  the  fact 
of  their  successful  treatment  of  such  a  difficult  veinstone  for 
so  many  years.  To  properly  understand  the  magnitude  of 
the  work,  suppose  we  estimate  the  yield  of  the  veinstone  in 
California,  from  all  the  mines  in  pyritic  matter,  to  be,  say  five 
per  cent,  of  all  that  is  worked  (which  is  rather  high),  it  will 
hardly  equal  that  treated  daily  at  the  St.  John  del  Rey 
works. 

The  results  of  years  of  experience  in  working  such  a  mine 
ought  to  be  interesting  even  if  it  were  not  exceedingly  valu- 
able, as  it  really  is  ;  yet  there  are  not  wanting  those  who 
object  to  any  information  obtained  from  the  reports  of  such 
as  the  St.  John  del  Rey  Company,  on  the  (not  very  wise) 
grounds  of  the  mine  being  worked  in  Brazil,  and  the  reports 
printed  and  published  in  London  ;  and,  may  be  worse  than 
all,  that  the  dividends  are,  and  have  been  for  the  last  forty 
years,  paid  there.  In  the 

MILLING   OF   CALIFORNIA   GOLD   QUARTZ, 

I  would  advise,  for  low  grade  rock,  the  stamping  of  it  as 
coarse  as  such  a  machine  as  the  "Frue,"  or  other  improved 
concentrator  can  treat  to  advantage.  The  size  of  the  aper- 
ture in  the  screens  should  gradually  increase,  and  be  the  larg- 
est in  the  upper  part,  which  would  in  a  great  measure  prevent 
what  is  termed  "dead  stamping,"  and,  at  the  same  time,  add 


greatly  to  the  duty  of  the  stamps.  Screens  having  12  holes 
to  the  linear  inch  in  the  bottom  and  10  in  the  upper  part, 
are  not  too  coarse  for  low  grade  rock.  As  a  stamp-head 
weighing  8  cwt.  will  then,  on  an  average,  reduce  4  tons  in  the 
24  hours,. and  those  of  6  cwt.  about  3  tons,  and  any  trifling 
loss  of  free  gold  will  amply  be  made  up  by  what  is  saved  in 
the  sulphurets — so  that  a  "Ten  Stamp  Mill"  with  heads  weigh- 
ing 8  cwt.,  can  be  made  to  ivork  to  advantage  4.0  tons  of  rock 
per  day.  The  fineness  of  the  stamping,  however,  is  in  part 
regulated  by  the  position  of  the  screen,  that  is,  their  hori- 
zontal distance  from  the  stamp-head  and  the  vertical  height  of 
the  bottom  of  the  screen  above  the  level  of  the  die.  For 
example,  the  finest  work  is  done  by  splash-stamping,  that  is, 
without  using  any  screens,  and  allowing  the  pulp  to  be  dis- 
charged over  the  front  side  of  the  mortar,  which  is  purposely 
made  lower  than  the  back  or  feed  part  of  the  mortar. 

The  Port  Phillip  Company,  in  Australia,  I  believe,  use 
them  with  10  holes  to  the  linear  inch.  Steel  wire-cloth  is  the 
best  and  will,  I  am  told,  last  better  than  any  other. 

Some  years  ago,  in  a  communication  to  the  State  Geolog- 
ical Society  on  the  subject,  I  recommended  fine  stamping  for 
low  grade  rock  containing  a  large  proportion  of  sulphurets  ; 
but  recent  improvements  in  concentrators,  and  a  closer  exam- 
ination of  the  condition  of  the  gold  in  the  iron  pyrites,  of 
which  I  find  so  large  a  proportion  is  in  thin  films,  and  which, 
with  a  rapid  flow  of  water,  would  be  carried  away,  and  a 
greater  part,  of  it  lost,  have  altered  my  opinion  on  this  point. 

It  is  not  generally  known,  but  nevertheless,  from  numerous 
and  very  careful  tests,  it  is  proved  that  in  fine  stamping, 
when  the  speed  of  the  stamps  is  above  seventy-five  blows  per 
minute,  that  the  loss  of  gold,  when  blankets  or  raw  hides  are 
used,  is  much  greater  than  at  a  speed  of  fifty  blows  per  min- 
ute; though  I  am  not  aware  that  any  tests  have  been  made 
when  the  amalgamation  was  done  in  the  battery.  The  sys- 
tem of 

AMALGAMATION    IX    THE   BATTERIES, 

However,  I  have  always  considered  a  mistake  and  as  entails 
ing  a  great  loss  of  gold,  particularly  so,  when  the  rock  con- 
tains a  large  proportion  of  sulphurets;  besides,  if  precaution- 
are  not  taken,  a  low  degree  of  temperature  will  render  the 
amalgamated  silver  plates  nearly  useless.  To  understand 
this  correctly  let  the  mill-man  put  two  or  three  barrowfuls  of 
rock  very  rich  in  sulphurets  through  the  stamps  and  then 
watch  the  effect  on  the  amalgamated  plate,  and  at  the  same 


-  15  - 

time  collect  some  of  the  pulp  after  passing  over  the  plates, 
and  have  it  carefully  tested,  and  he  will  then  better  under- 
stand why  I  prefer  the  blanket  system. 

Prof.  W.  W.  Smyth,  in  one  of  his  lectures  on  gold,  with 
respect  to  stamping,  says :  "  Take  a  large  hammer  and  gently 
crack  a  nut  with  it,  and  you  have  an  illustration^of  what  a 
stamp  ought  to  do;  it  ought,  if  possible,  to  crack  the  envel- 
oping shell  of  stone,  and  set  free  the  kernel  of  metallic  min- 
eral unbroken'."- 

Or,  for  instance,  take  a  piece  of  veinstone  from  the  Bodie 
district — the  same  as  marked  No.  26 — one  half  of  it  pound 
very  fine,  using  a  grinding  action  with  the  pestle,  then  wash 
out  the  gold  in  a  batea,  or  horn  spoon,  and  you  will  find  that 
a  large  proportion  of  the  gold  will  float  away,  in  spite  of 
every  care,  even  using  ammonia  to  destroy  the  grease  on  the 
ends  of  the  fingers. 

Then  take  the  other  half,  pound  it  very  coarsely,  and  in 
washing  out  the  gold  you  will  see  very  little  float,  and  two  or 
three  turns  of  the  batea  will  bring  all  the  gold  into  the  center. 

IN    THE   BLANKET   SYSTEM, 

Where  improved  concentrators  are  used,  after  the  pulp  has 
passed  over  the  blankets,  only  two  lengths  of  trays  of  about 
four  feet  each,  and  two  sets  to  each  five  stamps  are  required. 
They  should  be  so  arranged  that  the  inclination  can  be 
altered,  say  from  3°  to  5°,  to  suit  the  stuff  being  treated. 

The  trays  should  be  about  16  inches  wide,  and  the  fall  from 
the  battery  box  to  the  head  tray  the  same  as  from  one  tray 
to  another,  about  4  inches,  with  a  board  placed  across  the  end 
that  the  fall  of  the  water  or  pulp  will  be  so  broken  as  to  strike 
the  blanket  in  the  tray  below  nearly  at  right  angles.  The 
blankets  should  be  in  3-feet  lengths,  and  made  of  coarse  wool 
with  a  long  nap.  The  double  sets  of  trays  are  for  the  con- 
venience of  changing  and  washing  the  blankets.  The  blanket 
washings  can  be  passed  through  a  simple  machine  like  that 
described  in  Phillips'  Metallurgy  (see  page  185),  and  the  tail- 
ings from  it  ground  with  the  coarse  concentrations  in  a  Chil- 
ean mill. 

It  is  not  so  much  the  length  of  the  blankets  that  separates 
the  gold  from  the  gangue,  but  the  fall,  or  jump,  on  them. 

Where  the  mill  has  a  limited  supply  of  water,  and  they  do 
not  like  to  go  to  the  expense  of  a  number  of  concentrators,  a 
coarse  concentrator  may  be  made  with  a  "  Tye  Buddie,"  the 


-  16  - 

plans  and  directions  for  the  use  of  which  will  be  found  in 
"Phillips'  Metallurgy  of  Gold  and  Silver,"  page  187. 

The  concentrations  from  the  "Tye"  can  be  passed  over  the 
"Frue,"  one  of  which  would  then  be  sufficient  for  a  large  mill; 
though  I  am  not  prepared  to  say  by  such  means  they  can 
work  as  closely  as  by  using  the  "Frue"  alone. 

In  case  the  mill  is  not  situated  at  a  very  great  altitude, 
where  the  frost  might  interfere  with  this  working, 

AMALGAMATED    PLATES, 

In  3-feet  lengths  and  2  feet  deep,  on  a  fixed  frame  at  an 
angle  of  about  3°,  to  which  a  slow  lateral  movement  backward 
and  forward  of  orfe  foot,  together  with  a  slight  shake,  is  given, 
in  the  same  direction,  with  a  sprinkling  of  clean  water  from  a 
perforated  pipe  falling  on  the  upper  part  above  where  the 
pulp  strikes,  might  be  placed  with  advantage  between  the 
blankets  and  concentrators. 

THE   CONCENTRATIONS 

Should  be  sifted  through  a  seive  having  80  holes  to  the  linear 
inch,  and  any  particles  that  were  not  fine  enough  should-  be 
ground  in  a  Chilean  mill,  the  same  as  described  by  Mr.  Latta, 
but  without  using  the  mercury;  and  afterwards  charged  into 
wooden  barrels  for  amalgamation;  but,  before  charging,  the 
sulphurets  should  be  soaked  in  water,  to  free  them  from  all 
decomposition.  I  feel  confident  that  larger  results  will  be 
obtained  by  thus  treating  the  raw  ore  than  if  it  was  roasted. 
The  great  difference  between  a  wooden  surface  and  a  metal 
one  in  amalgamation  can  easily  be  shown  by  washing  out,  say, 
about  one  dwt.  of  Bodie  or  Grass  Valley  gold  in  a  batea  and 
then  adding,  with  a  dropping  bottle,  just  sufficient  mercury 
for  it  to  amalgamate  jvith — too  much  or  too  little  will  lengthen 
the  result ;  but  if  the  proper  quantity  be  used,  by  rubbing  it 
with  the  finger  in  the  center  of  the  bowl  it  will  amalgamate 
rapidly  in  less  than  a  minute.  Try  the  same  experiment  with 
an  iron  pan,  and  you  will  find  how  much  longer  it  takes  to 
get  the  same  result.  I  would  strongly  recommend  any  mine 
adventurer,  before  erecting  any  quartz  mill,  or  adopting  any 
particular  process,  to  have  some  20  or  30  tons  of  the  rock  or 
veinstone  stamped,  and  to  save,  during  that  operation,  a  fair 
sample  of  the  battery  pulp  from  it,  which  should  be  carefully 
concentrated  in  a  batea,  or  any  other  utensil  used  for  washing 
on  a  small  scale.  The  condition  and  quantity  of  the  gold, 


and  other  ores  and  minerals,  should  be  tested  and  examined. 
The  percentage  of  the  sulphurets  can  also  be  roughly  esti- 
mated at  the  same  time,  and  all  afterwards  compared  with 
the  gross  results  from  stamping. 

TEST   FOR    TELLURIUM. 

Mr.  Edward  Booth,  analytical  chemist,  has  kindly  furnished 
me  with  directions  for  making  a  simple  test  for  tellurium,  in 
case  telluric  gold  is  suspected  to  be  mixed  with  the  sulphu- 
rets. It  is  as  follows : 

"Place  in  a  test  tube,  or  other  vessel  capable  of  resisting 
the  action  of  acids,  a  small  amount  of  the  suspected  material; 
which  has  been  separated  as  thoroughly  as  possible  from  the 
accompanying  gangue.  Add  enough  sulphuric  acid  to  well 
cover  the  sample  and  heat  to  boiling.  If  tellurium  is  present 
the  liquid  becomes  colored  a  clear  purplish  red." 

I  have  only  found,  as  yet,  telluric  gold  in  two  mines  in 
Nevada  County — one  near  Grass  Valley,  and  the  other,  the 
Murchie  mine,  near  Nevada  City.  - 

In  my  private  collection  I  found  a  specimen  marked 
"Meadow  Lake  Ore."  I  do  not  /ecollect  who  gave  it  to  me, 
but  it  contains  both  gold  and  telluric  gold. 

REBELLIOUS    GOLD   ORES. 

A  great  deal  has  been  written  and  said  about  the  so-called 
rebellious  gold  ores  of  the  Meadow  Lake  District,  and  what 
the  different  process-m'en  were  going  to  do  with  them,  but  I 
never  remember  having  heard  of  any  careful  analysis  being 
made,  either  of  the  veinstone  or  the  concentrations.  I  .would 
therefore  respectfully  suggest  to  those  who  have  any  samples 
of  the  Meadow  Lake  ores  to  donate  them  to  the  State  Mining 
Bureau,  as  the  examination  and  determination  of  them  would 
be  of  the  greatest  importance  to  the  mining  interests  of  the 
State.  The  mines  were  discovered,  I  think,  in  1862,  and  in 
1865  and  1866  eight  quartz  mills  were  erected;  a  large 
town  built,  estimated  to  contain  5,000  inhabitants.  Now  the 
place  is  quite  deserted. 

In  the  published  reports  of  the  Geological  Survey,  1864, 
by  Professor  Whitney,  no  mention  is  made  of  the  mines  or 
district,  so  that  little  could  have  been  known  about  them  at 
that  time. 


-  i8  - 


THE   PAN    SYSTEM. 

I  can  only  now  add,  that  had  I  years  ago  acted  upon  what 
I  now  suggest  to  others,  I  would  have  saved  large  sums  of 
money  for,  my  partners  and  myself.  For  instance,  what  is  the 
difference  between  the  gold  and  sulphurets  in  the  Mammoth 
lode,  Mono  County,  and  in  the  Sierra  Buttes  lode?  Is  not 
the  gold  in  the  latter  much  more  difficult  to  save,  and  would 
not  the  Comstock  soda,  salt,  and  pan  system,  if  introduced  at 
the  Sierra  Buttes  mine,  soon  close  it  up  like  the  former?  For 
my  own  part,  I  firmly  believe  that'  if  the  same  pan  system 
were  used  in  the  Victoria  District,  Australia,  all  the  mines 
using  it  would  soon  cease  to  pay  dividends;  and,  also,  if  the 
Idaho  mines  at  Grass  Valley  were  to  try  it,  that  their  divi- 
dends would  soon  be  reduced  one  half. 

If  the  correct  number  of  tons  of  mercury,  soda,  salt,  and 
"other  chemicals,"  as  they  are  called,  that  have  been  sent  to 
the  Mono  County  mills  were  published,  I  am  afraid  it  would 
appear  to  be  very  large. 

It  might  be  urged  that  the  chemicals  used  in  the  Bodie 
mills  were  for  the  extraction  of  the  silver  from  the  ores.  In 
that  case,  it  would  be  exceedingly  interesting  to  ascertain  the 
expense,  and  see  if  it  did  not,  as  some  think,  cost  $2  in  coin 
for  every  $i  in  silver  so  obtained. 

CATALOGUE   OF    SPECIMENS. 

The  following  is  a  catalogue  of  the  specimens  which  I  shall 
place  in  the  State  Mining  Bureau  to  illustrate  this  paper: 

No.  i — Crystal  of  pyrite  on  a  glass  slide.  Some  of  the  faces  are 
very  finely  and  beautifully  gilded;  so  fine  indeed  that  it  requires  an 
inch  objective  to  see  it  to  advantage.  From  the  Eureka  mine,  Grass 
Valley. 

Nos.  2,  3,  and  4 — Gold,  in  little  drops  or  specks,  imbedded  in  the 
pyrites.  From  El  Dorado  County. 

No.  5 — A  specimen  of  arsenical  pyrites  with  gold.  From  a  mine 
near  Nevada  City. 

Nos.  6  and  7 — Sections  cut  from  the  same,  in  which  the  gold  is 
easily  recognized. 

Nos.  8  and  9 — Gold,  with  telluric  gold. 

No.  10 — Section  cut  from  same. 

No.  ii — Gold  in  carbonate  of  lime.      P^ureka  mine,  Grass  Valley. 

No.  12 — -Gold  in  talcose  slate.     Taquarilla  mine,  Brazil. 

No.  13 — Gold  in  talc.      Placerville. 

No.  14 — Gold  on  talc.      Brazil. 


-  19  - 

Nos.  15  and  16 — Gold  in  lacotinga  (micaceous  iron).  Gongo 
Soco  mine,  Brazil.  The  lac^irrja  veins  are  from  a  few  inches  to 
many  feet  in  width. 

Nos.  17  and  18 — St.  John  del  Rey  veinstone;  18  is  about  the 
average  of  what  was  milled  in  1866. 

No.  19 — Specimen  of  killas  from  St.  John  del  Rey  mine;  a  rock 
which  forms  the  sides  of  the  lode,  but  also  contains  considerable 
pyrites. 

Nos  20,  21,  and  22 — Sections  cut  from  St.  John  del  Rey  vein- 
stone for  microscopic  examination. 

Nos.  23  and  24 — Sections  cut  from  the  killas. 

No.  25 — Yellow  dusty  matter  mixed  with  gold,  taken  out  of  one 
of  the  richest  pockets  ever  found  at  Grass  Valley. 

No   26 — Veinstone  with  gold.     Bodie  District. 

No.  27 — Gold  in  country  rock  (diorite).     From  Nicaragua. 

No.  28 — Gold  in  quartz  crystal. 

No.  29 — Gold  in  syenite. 

No.  30 — Section  cut  from  No.  29. 

I  have  cut  a  great  number  of  sections  from  the  St.  John 
-del  Rey  veinstone,  but  could  not  detect  the  gold  in  any  of 
them,  and  unless  very  great  care  is  taken  the  batea  test  will 
hardly  show  any  gold ;  notwithstanding  which,  on  a  large 
scale,  they  obtain  better  results  from  the  amalgamation  of 
the  raw  sulphurets  than  any  other  process  I  have  seen  tried. 

THE   TRIBUTE    SYSTEM. 

I  have  just  received  a  copy  of  the  report  of  the  Port  Phillip 
Company,  Australia,  published  January  13,  1881,  by  which  it 
appears  the  tribute  system  has  been  introduced  there  with 
great  success.  Too  much  can  hardly  be  said  in  favor  of  such 
a  system,  as  it  places  the  hard  working  and  intelligent  miner 
on  a  much  more  respectable  and  independent  footing;  and 
though  he  in  a  measure  shares  the  risks,  but  only  so  far  as 
his  judgment  guides  him,  he  gets  the  benefit  of  any  discovery 
he  may  make.  It  also  encourages  him  to  study  the  peculiari- 
ties of  the  lode  and  inclosing  rocks ;  besides  which,  by  that 
system,  all  are  jointly  interested  in  the  welfare  of  the  mine. 
Many  of  the  mines  now  idle  in  this  State  could  be  worked 
profitably  under  the  system,  particularly  in  the  Bodie  district. 

In  the  Port  Phillip  report  it  says: 

The  number  of  tributes  has  averaged  about  200  during  the  year, 
which  shows  no  decrease  when  compared  with  the  preceding  year. 
The  tribute  system  has  been  further  extended  by  an  arrangement 


-    20   - 

with  the  tributers  to  drive  the  levels  in  the  ground  let  to  them,  the 
company  assisting  them  with  driving  timber  and  rails,  and  making 
an  allowance  per  fathom  until  the  yield  reaches  6  dwts.  per  ton, 
when  no  further  assistance  is  given;  the  company  receiving  half  the 
gold  obtained,  and  deducting  from  the  allowance  the  cost  of  tram- 
ming. By  this  means  a  large  amount  of  driving  is  done  at  a  com- 
paratively small  cost. 

The  number  of  tons  of  quartz  stamped  on  tributers'  account 
for  the  year  was  48,184  tons.  The  average  yield  of  the  entire 
quantity  raised  was  5  dwts.  5^  grains  per  ton  (say  $5). 

Total  receipts £82,364  14s  7cl 

Expenditure 26,310  10s  7d 

Leaving  a  profit  of £0,054     4s  Od 

In  conclusion,  so  thoroughly  am  I  convinced  of  the  great 
benefits  that  would  result  to  this  State  by  a  more  general 
introduction  of  the  tribute  system  in  an  extended  form,  both 
to  the  placer  as  well  as  vein  mining,  that  I  wish  particularly 
to  call  your  attention  to  it,  so  that,  through  the  influence  of 
the  Bureau,  the  subject  may  be  brought  in  a  proper  light 
before  the  owners  of  mines  or  claims.  A  fair  tribute  will 
secure  the  muscle  of  the  working  miner,  who,  in  too  many 
cases,  understands  better  than  the  Superintendent  (generally 
a  man  of  business)  how  to  conduct  trials  for  ore,  and  after- 
ward to  develop  them.  The  muscle  of  the  skilled  miner  is  in 
every  respect  better  than  foreign  capital. 

There  is  no  need  of  the  hard-working  miner  to  leave  this 
healthy  climate  in  search  of  employment,  if  those  who  own 
mines  that  are  now  idle  would  let  the  fact  be  known  through 
the  press,  and  at  the  same  time  offer  a  fair  tribute  for  working 
them. 


14  DAY  USE 

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